Find a gunsmith.
OK
A thousand or so.
18mm
Whatever your willing to pay for it.
50-200
100-5000 USD depending on specifics
8mm
m = 15
Not likely. No sn data in published form.
Leinad221 Hwy, 68 NorthP.O. Box579Ducktown, TN 37326(423) 496-7060Try Cobray for older parts; Telephone: : Technical Support: 701-245-6414 : Toll Free Ordering: 800-861-1323 ; Fax: 701-245-6579 : ; Postal address : Cobray Company395 2nd Avenue EastWesthope, ND58793-4128 ; Electronic mailGeneral Information: cobray@cobray.comTechnical Support: support@cobray.com
M12 signifies that the shank is 12 mm diameter. The length will vary. +++ Another tip: The A/F size of a standard M12 bolt or nut is 19mm, so close to 3/4" that the latter spanner will work - but be aware that this is the only co-incidence between metric and inch-based fastenings; and the M-series proportions don't follow a very consistent path!
Blue Book of Gun Values