If you have a lot of $$ to spend, get a Retul fit by Josh Frick at CycleLife in Georgetown. There are some other people who come into the area to do Retul fits, but generally those come up with special club deals.

Other less expensive fits to be had at Revolutions (Clarendon location might be best for this), Spokes etc. on Quaker Lane in Alexandria.

You can also go to Quest or Capital Bicycle in Annapolis.