Your best bet is a working and fully functional Model 10, 15, 64 or 67. Gunbroker typically has quite a lot of these in varying conditions.

Whatever they will teach and you will learn in the class you take will work absolutely as well if you go in there with a functional K-38 as with a "needs repair" Model 10. A patient buyer can snag a functional K-38 for around $250-$300.

To add if you did not know:
Model 10 = k-frame .38 blued, fixed sights
Model 15 = k-frame .38 blued adjustable sight
Model 64 = k-frame .38 stainless fixed sights
Model 67 = k-frame .38 stainless adjustable sight

Functionally and internally, all four are the same.