I think it's wonderful that you want to honour your grandfather in this way, perhaps you could wear a piece of tartan behind your badge on a Balmoral or a Glengarry if you have one. Flashes as you already mentioned would also be an idea. I know you said you do not have the means for a kilt at the moment, but I thought I'd throw this out there for you. Burnett's and Struth have the RCAF tartan in their casual sale here is the link
http://www.burnetts-struth.com/produ...oducts_id=1239

Perhaps when you do have the means this would be one way to go.