Indeed transistors / MOSFETs in SOT223 package are somewhat uncommon. However, since SOT223 is fairly large, you may consider using through-hole replacements. Just bend the pins close to the transistor body, and solder them onto the PCB pads. I’ve done this before and it works well.
If you are going to interface with inductive load (such as DC solenoids), you may find it easier to just get one of those relay boards (http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=relay+board). Will save you a lot of work of having to solder the flyback diodes.