Base Scrapper's mods are 25% SDI, FC/FCR 1 & LMC 10%. You cannot get one with better stats on those properties.
Other mods you can get are increased skills (resist, magery, eval, med), mana or int increase, LRC, and mana regeneration +1. Slayers are also possible, but any decent one (or a super slayer) would be worth a fortune. Up to three additional mods are possible, but the triple ones are rare.
The most common 'decent' ones that come up for sale are those with two skill increases. These seem to sell for 1 million plus.