Considering the obscene price of gold - why not gather up some old gold (your wife will be happy to make a contribution to your new bling) and take it to the jeweller doing this work to offset some of the costs, which will be considerable? This will be a big bullet to bite.

Also - historical note - from the Magna Charta - to the Act of Union between Scotland and England - signet rings have been used alongside signatures. Long tradition here.