In my experience, in instructing and coaching for over 15yrs, and religiously using trainer 22 pistols, I'd not concern yourself with matching identically your full caliber firearm with your trainer. Having similarly located manual of arms is a slight advantage, but should not be a necessity. The important factor of the 22LR trainer is to choose a model which "removes all alibis and excuses," meaning it should have a sufficient barrel length such sight radius is not a problem, should have sufficient sights such picture is not a problem, should have a size such sufficient grip is not a problem, should have sufficient weight such recoil is not a problem, and should have a sufficiently good single action trigger such trigger management cannot be a problem... And of course, they need to be sufficiently inexpensive such they're not cost prohibitive to own and maintain - these should be shot FREQUENTLY (start every session with this pistol), so they will take wear and require service as a matter of standard preventative maintenance and repair.
As such, in my experience, the best advantaged 22LR pistol trainer is a target style pistol: Ruger Mark series, Browning Buckmark, Beretta U22 NEOS, S&W Victory, etc. Combat style 22 pistols like the S&W M&P22, Ruger SR22, Sig Mosquito, etc are very fun pistols and are a lot of fun, but I have not seen the same advantage for shooter development with these as I have for target style pistols. I have not personally seen, as an instructor or a shooter, the conversions offer a significant advantage either. I have 1911 and Glock conversions, and outside of competition specific training, I have not seen these to be a significant advantage over a target style conventional 22 LR pistol - and of course, these conversions often cost as much, or nearly so, as a dedicated 22LR pistol, so outside of competition, I can't say I recommend them.