Check the browning bps... Cost is on par with rem 870 wingmaster. Trigger isn't as crisp, but it has bilateral symmetry, perfect for left or right hand shooters.
I like the BPS and a danged fine shotgun it is, but it's not capable of being topped off from the ejection port as the OP wants since it ejects out the bottom. Me, I'm a Mossberg fanboy BECAUSE I shoot lefty. Actually, I'm right hand dominant, but left eye dominant. I even shoot right handed bolt guns left handed. If you need a second shot, you didn't do it right.
But, I'm pretty fast on the bolt with my right hand. being right hand dominant and I'm afraid it'd take me a while to get used to a lefty.
On my Winchester 1400, I installed a left hand safety, safety is out front of the trigger guard and that's a good thing. My trigger finger has kicked the right hand safety ON before on a Remington, which has the safety behind the trigger guard, and caused a few ducks to get away. Irritating, and it's irritating when a teal buzzes in fast and low and you have to reach UNDER the trigger guard to get the safety off. By that time, the bird is out of range. THAT is a problem with right handed crossbolt safeties and me. No thanks on that. Admittedly, this was with the Winchester, but the less movement I have to make from port arms when a bird is coming, the better.
Generally the safety on the Mossberg falls off or will break at the time you need the gun the most.
The plastic will break or the screw holding it will fall out, when that happens you now have a poor boat paddle! Parts inside jamb the hammer and trigger.
I'll stick with my Mossbergs. I have a 20 year old 500 camo I've been hunting HARD in salt marshes with for 20 years, never a problem with the safety and it's lighter than a BPS and gets to the shoulder a little quicker, though I'll grant you the BPS is a fine waterfowl gun. None of the above bovine excretion has ever happened to MY Mossbergs, not in 30 years of hunting with Mossbergs and when I was younger I hunted every season like I was Phil Robertson, but on foot in the salt marshes or in boats on the bay and rarely from a nice blind, often huddled in the salt grass. That's why I like 'em, they're rugged to the max, don't turn to rust at the hint of salt water like the 870 Express, and the ergos, especially for a lefty, are fantastic. The shell elevator is out of the way like a BPS on loading the magazine, doesn't bite the finger that feeds it on a cold morning. The slide release is where it's supposed to be, where you can get at it without looking....even left handed. The ONLY more lefty friendly gun is the BPS, but right side ejection doesn't bother me.
I bought a 535 Mossberg a couple of years ago at a pawn shop for $170. It's basically a 500 that shoots 3.5". It was like new except somebody had cut the stock by an inch to make it 13" of pull and didn't trim the recoil pad. I shaped the pad to the stock and put a slip on Limb Saver on it to get the thing back to 14" LOP. On Mossbergs, I always have to shim the stock to get proper drop at comb to fit me, but that's easy enough. She shoots fantastic and a bonus, I can pull the limb saver off it when I'm wearing heavy winter clothing in cold weather. I like this thing, have shot doves and ducks, but not geese, yet. I haven't patterned a box of T steel 3.5" in it, yet, and doubt it'll pattern as well as the 90+ percent my 10 gauge H&R (lefty friendly, of course), but if the 535 patterns over 80 percent, I may use it on my next goose hunt to try it out. It's a lot lighter than the 9 lb H&R, though, so if it hurts too bad with 3.5", well, I might rethink this. LOL!
I don't even notice the whole shotgun, regardless of brand, when I'm shooting it, let alone the safety. You must have never picked up a Mossberg. The safety is below the line of sight of the rib when properly fitted. Even if it points high (less drop), the safety wouldn't be in the line of sight.