If you have a scanner, then scan the gaskets you make or buy and if they fit well...and you also measure the thickness of the paper or whichever material it happens to be, then you can cut your own from those patterns. A little double stick tape or glue stick can temporarily adhere the pattern to the gasket material... Use punches for your holes and a good sharp blade.
Sometimes you can make your own set cheaper than you can buy them if you only need a few...certainly would not be applicable for gaskets that are critical they not leak or fail...
A dab of grease on paper gaskets can help keep them in place when reassembling when bolts go through the gasket or fit it to the cover you are putting on first. If the sealing surface has PO damage with a gouge to the sealing surface, then level it with a file or sanding block and then on a flat surface, 1/4" glass works great, you can tape a sheet or two of fine sandpaper to level that cover to a good sealing surface again. This only works on covers which do not have clearance issues that are very tight or another part such as a clutch cover and clutch mechanism might be slightly affected. If the gouge in a sealing surface is too deep or in the cases, then you can use JB Weld as it is an excellent alternative and commonly used by many. FWIW, FYI...
You can buy all kinds and thicknesses and sizes of gasket paper and gasket material on Ebay or McMaster-Carr, Amazon, etc.
Personally, I try to avoid Chinese parts...but so much any more is being made there and some of it is of good quality, if they were built to a quality level rather than a price point or they were counterfeit. There are lots of cheap electronics that are made from recycled electronic components...bet that is not commonly known. Sometimes it is not a bad thing as it is low risk, but other devices should not be used that are recycled. Capacitors and IC chips can be some of the more risky common components/devices harvested... Another tidbit...
Good luck with your build... there are several 650 build threads where they are dropping a rebuilt 650 motor into a 550 frame. A very nice modification as the 550 is a nice handling chassis with some improvements it is even better.
You can check into those, they have done much of the legwork on gaskets and sources and can advise you...
Camrector is one of those individuals... GV1390 and DaveBarbier are a couple that are doing the 650 in 550 frame.
David