Sooo promise ring/necklace for guy

This isn't asking about anyways opinion on promise rings. Ik some people think it's like high school and all. My bf and I have been dating 3 years and 2 of those have been long distance. Going in we had no idea if it was gonna work but somehow we are making it work and great. So next month is our 3 years he offered to get me a promise ring ( I have always wanted one just cause I think it's cute). This is going to be under 50 and nothing expensive. But I want to get him something similar he always wear a necklace with a saint on it so idk do I get like a charm?? He said he wouldn't wear a ring. Is there a way to get something matchy. Has anyone done something similar?