I have been making my own extensions for years. I use a Molex universal crimper that will do several sizes of terminal crimps.
https://www.waytekwire.com/item/539/...FVI8gQodChwFRw
Here is a ratchet type also, will not do all sizes but should cover the standard hobby terminals.
https://www.moddiy.com/products/Prof...FVA9gQodkwYHeA