I understand your question, but, I decided to go with a little different approach. I drilled 1 little hole in the foregrip, installed a sling swivel stud, then mounted a bipod to the stud. Looks and works great! However, to answer your question directly, I do not know of a barrel band rail, yet.
UPDATE! There are a variety of barrel band rails available for the prod as well as other brands of airguns. Amazon, Ebay, etc. Just Google it, lots of options available.