I have a mildly expensive, but beautiful, solution.
Buy a GPS speedo from speedcafe.com and then have your local instrument fitter put the GPS speed "guts" into the standard BMW Speedo "can".
The pesky speedo cable can then be dispensed with and a suitable cap purchased and installed.
My own view of my R65 is that originality is important and where original parts cannot be sourced then something that looks OEM is better than something that does not, note that this is a personal view and not shared by many other r65 owners.
There is a good write-up in the BMWOA forum from a guy who installed one in his R80 G/S - this was what caused my ears to prick up as the early model R80 G/S used the same speedo as R65/R80 S/T and many R65 speedos ended up in G/Ss due to their somewhat higher "consumption" of such items.
Anyway, with a selectable "hot start" you get virtually instant start up and the sampling rate is to my eye about the same as the response time for a cable driven speedo.
A further alternative is to simply purchase one of the automotive "HUD" GPS dashboard speedos (preferably one that can display in normal or mirrored text) and velcro that to your instrument panel. A decent one will have no difficulty with the heat and should be waterproof - costs start at around $80 out of China.
Final alternative - there are still reasonable stock in the USA of R65 MPH speedos with the 80mph max and the enlarged 55mph - I am using one of these myself with GPS checked marking for 60/80/100 kph and calibrated eyebrow extrapolation elsewhere.
