You can experiment with rubber bands or velcro. I'd suggest trying to add some pressure to the dorsal vein area - maybe glue a ball bearing to some velco - to see if you have success. Then you can invest in a high quality ring like the ones from from allknight.
That's a good idea to add some kind of bump/ball to the top of a velcro strap.
Will give that a try - thanks.
J