You're just remembering and missing your Mom. I don't think it's selfish to wonder what she would have gotten you. And the more unusual the gift the more it's remembered. Even if she did get it at a yard sale.....it's the thought that counts and, more importantly, it was from her and she was specifically thinking of you when she got it. I'm sure that means more to you than anything does.
Emotional days will always be here for those of us who have said goodbye to loved ones. It's just the love we feel for them still shining through. Time will soften the edge and those memories will eventually be a comfort to you.
You're in my prayers, Doydie.