Quite simple and cheap to make.

I use one of those same pumps as the accu-products uses. Can get them from the medical store for peanuts. Made a plug for the insulator out of aluminium, but another way to do it is to use an old insulator and just fill up the bit where the carb plugs in with epoxy steel, let it set and pop it out. A bit of wax on the insulator first will ensure it doesn't glue itself in there. Then you have a perfect shape part. Drill and tap this to fit the gauge and pump etc.

To block the exhaust I roughly sawed a plate of 10mm aluminium, drilled a couple of holes and use a big fat o-ring (from the plumbing department) to seal it.

Screw in a spark plug and you're ready to rock.

Just make sure you get a reasonably low pressure gauge. I see the accu-product gauge reads 15psi, which is perfect so that you can easily see any drop in pressure.