Just rim it yourself, it's not really a hard process. If you don't want to trim it because you fear you'll lose your rom in the process, then don't fret, most trimmer leave a backup of the original rom (I can assure you NDS Tokyo Trimmer does). As Rydian said before, the amount of junk that's trimmed off depends on the rom; I know Pokemon White got a good 50MB off.
1-127MB actually... this is of course pending a 129MB game taking up a 256MB chunk. Btw, "NDS ROM Trimmer" is a really good ROM trimming application for anyone on a Mac (works with both Intel and PPC based Macs.)