http://www.realsteel.co.uk/
01895 440505
The place above stock Autometer parts and can get the bits on special order. You may want to double check the part numbers but from looking at the US sites I think I gave them the right details.
Autometer Metric Adapter 1/8" NPT to M12 x 1.75.
Product Code: 2278 - £10.34 + VAT
Autometer Replacement Sender Unit.
Product Code: 2259 - £18.52 + VAT
You are looking at a minumum of 6-8 weeks and because of this the guy I spoke to requires a cheque rather than credit card as people have ordered parts previously, got bored and cancelled the transaction leaving them with the stock.
I decided against this route at the moment opting for the magnetic plug instead.