I can refer you to a professional female keyholder in London who will hold your key for about £80-100/month ish (I'm not sure of her current rates). The expectation is that it is remote, possibly with audio or video calls. It's reasonable to expect that these will be somewhat limited in time for obvious reasons - probably daily or every other day checkins - but that would need to be discussed..
Having experimented with chastity for a while myself, you're best to engage a professional if you are not in a relationship. It's not *that* much money, and you know the person won't abandon you or lose interest part way through. IMHO the women online who are open to act as amateur keyholders will lose interest quickly, and you'll be left bored.
I also know a professional keyholder up North too who would also likely be able to help if the London one doesn't work.
PM me if interested in her details.