I would think that any local jeweler should be able to help you with sizing your finger. I would also think, an internet jeweler should be able to supply you with a ring sizer prior to purchasing their product. These are just my thoughts and I hope it helps you with your decision.
Steven
The problem we have at present is that jewellers are shut due to COVID, but we do have an excellent local one. The ring sizer is a good idea and one I’ll pursue on the Internet so thanks for that