Here is the one we use. I bought it at Canping World, but is is available all over the net.
etrailer.com has it for $120
Want to tow your boat or trailer and carry your bikes on your trip? This bike carrier allows you to do just that. Strong and durable, this bike rack fits securely over the ballmount for your 2" receiver.
Draw-Tite Towing Bike Rack from Swagman
3 bike carrier that mounts to the shank of a Class III, 2" square ballmount (not included).
Includes 3 Bolts to ensure a snug fit
A minimum 10" clearance is required between the hitch pin hole and the ball hole for mounting.
Use Ballmounts 2736, 80233 or D-28
Extra-Long Ballmounts with a Rise/Drop usually do not work because of the angled metal supporting the ballmount face.
Base of rack measures 3-1/8" long
NOTE: The trailer hitch's tongue weight capacity is reduced by the weight of the bike rack and the bikes when towing
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Paul & Helen:
We need to purchase a bike rack for our Gulfstream BT cruiser and also tow our car behind. What kind should I buy? </div></BLOCKQUOTE>