Reid, I can't recall ever seeing one.  I did make one up for a 3 prong 30
amp 220 dryer plug to a 30 amp 110 volt receptacle for an RV.  Be sure not
to go across the two hot legs and have both a neutral and ground connected.
On the 4 prong you should have both there in the plug.  On the 30 I had to
get a ground source.  Get good info on this and if you are uncomfortable
with it do not attempt it.  It isn't hard, but if done wrong could have
serious (possibly lethal) consequences.

Dave W.

Reid Fleming wrote: I have a 4 "prong" dryer plug in my basement.  Is there
a converter that will plug into it and let me plug in one or two 120VAC 30A
plugs?  If so, does anybody know of a place in the Vancouver BC area that
sells them?  If there isn't such a converter, how hard would it be to make
one up ?  Thanks!

Any electrician could make one up.
There are different configurations of plugs so draw what the dryer plug
looks like and give it to him/her.