Try
www.locksonline.co.uk or email enquiries@locksonline.co.uk or telephone +44 (0)845 2300201.
I was able to get a push button mechanism from this firm which while slightly different from that supplied in the original build, they exactly fitted in place of the mechanisms they replaced on my B36 from 2002 which probably has the same fittings as on your boat. The actual button push was re-used in each case as also were the rings surrounding the buttons so you would need to salvage them from the existing cabinets.
The mechanisms I bought last year had the following product code ART.309400, they were brown in colour and cost £3.32 each plus postage and VAT. I bought three and the total cost was £17.89 delivered from and to a UK mainland address.
By the way, I'm changing all of the original light fittings on my boat, if any are useful to you, let me know.