Try a 22 conversion kit for a standard firearm. This allows you to practice with the regular trigger pull and use your regular holster.
I liked my AA 22 for my Glock so much, I purchased another Glock just to permanently mount it. The original slide only has 100 rounds through it!
Advantage Arms 22 Conversion: Glocks and 1911's
The slide locks back on my Glock conversion.
Marvel Precision also makes a good product.