I've never needed more backstraps than the ones that come with it but I guess if you've lost one or something s&w is probably your best place to go to. For magazines I would suggest that you look online for SW99 mags. They work great in the P99 and are about $10-15 cheaper than P99 mags. As far as sights, it'll depend on the brand you want. I think the best choice is mepro night sights.