1) turn off the CAPS LOCK, please.
2) good luck finding a listing anywhere for a B250 slip-on or full-system. OTOH, if you just want a slip-on, you can cut the stock can off and slip on any can with the same pipe diameter... this is populat with the B400 folk, too. These bikes are generally too old for anyone to still carry something model specific.
3) a mph speedo from a B4 should be a bolt-on affair.