Personally I'd made one specific for my needs, but their are also some pretty decent ones out there on ebay (of all places) for a decent price ($75) item #370560164106. If you had a mill you could make one with a couple bucks worth of steel.
I've got a couple wrench's from the guy off ebay, i got them before i got into making my own stuff with my friends mill.
The best thing you can do is send it off to sombody that builds on Vanguards and Howas (same thing)the must torque those bastards on with a 4 foot cheater bar after a good bit of Rock Set.
Ive pulled the barrel off of 3 , the first one i ended up with a few hrs of metal work to the action due to it moving in the vice , yea that right i had to lock the action in a vise because the round barrel would not lock down tight enough. the next two to used a parting tool and made a reliefe cut very close to the action and it was MUCH easier to break loose but still harder than say a Rem or Win.
if i were gonna build on a Vanguard id send it to Mark Gorden at "Short Action Customs" , some other gmiths here may build on them but i dont know of any. Im sure Chad Dixon could to it after playing with a mouse and keyboard for a bit
If its blued, you just about have to part a line right in front of the action or try freezing the whole barreled action and warming the action up while leaning on the wrench, stainless seem to be easier.