I asked Glenn the same question last week as I was looking for some right angle fittings and he told me that most folks drill and tap them to a more standard and readily available size like 10/32.
Greg, I would love to even find some that are standard sizes. Does anyone even know what size the motor is currently setup for? It looks like a 4mm but not sure.
K&B still makes their 10-32 water fitting that curve about 60 degrees. They are great for 21- 45 engine because they are not too bulky and because they are curved they flow better than 90* fittings.
Call Gary @ G&M models 630-279-2451 He normally has them in stock as well as many other hard to find K&B parts.
Been a long time since I've needed any and I got mine from the rc boat company but when I checked their web page they no longer have the ones that I ordered so long ago, I would check where Andy suggests and see what you can find there.