I use my dog's old lead as a strap for my mandolin, tied to the head with a bit of string as there is no strap button on that end of the instrument. Works a treat!

I did, however, get some money for Christmas and podded out on a Levy strap for my bouzouki. I had to widen the hole a tad for the button which is also my amp socket, add an extra hole using a leather punch and make a little leather loop to stop the end flapping about, but it is now perfect - I wear it in sessions for hours and it is really comfy. Recommended if you have the bunce.