Gift certificates, are usually the way to go. How about a gift certificate for a massage, or a break at spa. How about cooking them a meal, or bringing them a meal from a restaurant. You can always get them, something they have been wanting for a long time. Moms are smart, and they will toss out their idea of what they want, when you visit often. I could hear my Mom say often, "Oh I need this ...", at many trips to the house. What you could do, is kill two birds with one stone. Get the thing she wants, on mothers day, even if she has to wait 8 months for it.. She may have been broadcasting her want, for a long time... Now, I maybe going to far towards my book humor on this one... I should stop, save it for the books..
It is hard to give something to a mother who has everything in her life. Me, or is that, you. You are her everything. So, be thoughtful, and spend even the afternoon with her, to make her day a great one, on Mothers day. As a man, I hate to use the word, but you could even say you... Lo..v...e.. Her... That was hard. :)
Have a good day, till next time....