I would like to source the following in 1/72 scale: .50 cals (preferably perforated barrels), 20mm Oerlikon, and single 40mm Bofors. These are for dressing up Revell 1/72 PT Boat which have really terrible weapons. Can anyone point me in the right direction?

RB Model is good place to start.

Master Models does 1/72 .50 barrels (brass)
Wespe does a couple different Bofors Guns in 1/72 and I think Zvesda does one in 1/72. White Ensign does Oerlikons in 1/72.

Biggles, if you haven't already, send Richard Harden of WEM a email, ask about the PT boats sets. I contacted him in late August about them, and he replied they were due out again in the near future.

https://www.whiteensignmodels.com/

The website lists all the items you are looking for, but still say 'out of stock', but would be worth checking with him

Jim F

When it comes to machine guns in Braille scale those from Miniworld are hard to top. Check hobbyterra.com to get an idea.
Whereever there is a machine gun on one of my 1:72-scale models I replaced them with one from miniworld.
(example: http://armorama.com/forums/216323&ord=&page=2)

Cheers Michael