I have a Dankoff pump [Flowlight Booster. For 20 yr.] The couple times I've needed something for it, I have been able to get it through a co. called Alternative Energy. I am in no way associated with them other than buying a few things from them. Talk to Bramley at 877.878.4060 ext145, he is the pump guy.
On something like this, I doubt they'd have it in stock, but they have ordered things for me from Dankoff and gotten it to me in a week or so. By the way, I've also spoken directly with the Dankoff folks when I couldn't figure out something. They have been quite helpful, but they do not sell stuff directly and will send you to someone such as AltE to order. They will give you an exact part # though, if you need it. I don't think you do, at this point.