you can try rcboyz for your bearing needs. and I believe the size you want for the diff bearings is 2.5mm . Remember though some recommend using them, others don't for the diff. So if they fail don't be suprised. I haven't had an issue yet with mine in the diff.
As for shocks, you probably can get them from a guy on ebay , I believe it is kprc , something like that. He puts alot of stuff up on ebay that looks like he took about a B4 kit to sell . he also has a website where you can buy it outright. I believe to buy it outright it costs 32.50 + shipping ( about $5 bucks? ) Most shops will sell you the front and rear shock kits that will work but you will spend about $60 retail on them. I also believe the B3 shocks in the rear hang lower than the B4 ones, if they hit the chassis I don't know. I think my B4 ones in the rear are dead on.
On a different note:
I called Tim at MRC yesterday to discuss a few things, pretty cool guy by the way! I told him about the axle shearing off and he is going to check with Academy and see what is going on with the axles. If any of you guys had this happen you should give him a call and see what he has found out, it is possible you may get a new set for free. He does have replacements in stock however.
I spoke with him about if he knew of any places that would carry Kose aftermarket parts and he told me that he is going to try and see if they could carry some of the Kose parts for the vehicle.
I hope that goes through as Kose has some nice stuff.