Is it possible to use a hose clamp and cable ties? I don't have a rack anymore, but I use the above combination to secure blinkies on my handlebars and on my seatpost.

If there is a tubular area with a large enough diameter, attach a small hose clamp to it. Loop several cable ties through both the clamp and the blinkie. A section of rubber cut from an old tire tube, used as a sleeve for the cable ties, will secure the blinkie snugly and prevent the hose clamp from cutting into the cable ties.