It might help your search if you could identify the tap maker and model. Reich and Whale are those typically used.
Whale used to have a second to none reputation in customer services though I heard that might have slipped. If they still are as old a call there with what you want would have resulted in the bit being sent FOC and a contented customer.
Reich's UK email contact is infoUK@reich-web.com, I cant comment on their customer services.
The aerators on my Reich taps are a very tight internal push fit; they are not screwed in my case.
If you can find an aerator that fits your tap, and you have an external water pump then I cant see any reason for not using it.
If its an internal positive displacement pump then there is just a faint chance of an issue.
Failing all that I would simply make one of the domestic type that are basically a concertina folded bit of metal shim. A very easy source of a scrap of aluminium shim is a beer can. Make sure its not steel.