If you truly want to do this mod I'd just keep my eye on Craigslist and run searches on VW, Karmann Ghia, VW parts, etc. The bumpers WILL come up. Getting two of them will take longer but that's all part of the fun of the build unless you have an unlimited budget.
EXAMPLE: (Took 30 seconds on my local Craigslist)
https://losangeles.craigslist.org/la...l<br />
<br />
https://orangecounty.craigslist.org/...833475905.html