Only patches i know of are the ones snes already mentioned, and there's a few german patches out there for the GBA SRT.
Alas afaik there's only a select few people working on english patches for SRT, so i wouldnt expect them anytime soon. and the few that you can find are just menu translations, and any SRT fan should know the menus. (or you could always mess with the menus and see what is what)
The menus are pretty easy to remember and even SP commands too. Luckily there's a wiki site called Akurasu that has a lot of translations and info for the SRW games (the newer ones have more info). Still the unit name patch is probably important for the GBA games as they didn't have a preview mech feature which probably meant that you'd deploy the wrong unit into battle.
No Mercy Zone - http://thenomercyzone.clicdev.com/f/ SRWG-W - http://www.srwg-w.org/
True, but he specifically asked about handheld games. Speaking of which there is also the very first SRW game (for the original Game Boy), but you aren't likely to find that very enjoyable even with a translation.