OK couple of things, oh and by the way, that is how I recover most all of my handgun lead as well, except see below....
1) You need to lay the bucket on it's side and shoot through the top. Lids are WAY easier to replace than the whole bucket. You can use just about anything to mend, repair, and possibly even replace those lids. I have used cardboard, paper plates, old paper targets that I don't shoot at anymore, such and so forth. All you need to do is keep the dirt from falling out. A little duct tape and whatever is handy is usually what works best.
2) I you want more portability look over at one of the big box hardware stores like Lowes or similar for rubber mulch. You might need another bucket to back up the first, I don't know, but it is MUCH lighter and you don't end up with a lot of extra dirt in your alloy. Maybe a little crumb rubber but it will at least burn off.
I get my buckets free from work so far. They get some water treatment pellets in them and after they are triple washed and rinsed, they are up fro grabs. They don't last long either. They have a nice screw on top which makes them great for anything or any type of dry storage.
I fill them with the sand at our farm which is almost like talc. Usually I do one or two in advance and will add in a half 16oz bottle of water, and screw on the lids and let them sit in the sun till we get back. This will fully saturate the sand inside similar to a terrarium. It is JUST right for stopping the bullets and makes sifting pretty easy as well.
You will also find a TON of other ideas, some of them are fairly simple and cheap, some of them are pretty exotic. Just click this link over to Castboolits,
Bullet-trap-ideas-for-recycling-lead