Yesterday, I bought a 50s/60s black dinner jacket orphaned from its pants. I’m wondering how to make up a full rig on a budget in London.

The options I've come up with so far are:

1) just hope to find pants in a similar used heavy unfinished worsted, even from Burtons who made the jacket, in a 30” waist by thrifting some more around London. Is there some very standard fabric used for DJs in the middle of last century which would make this easy?
2) get some made up from scratch from a similar weave - but it would be from a new bolt of fabric and might look v. different, like step-brothers. The only saving grace would be low-light evening events where the difference might not be obvious;
3) find or make a pair of white flannel pants, as I read has been worn before for evening-wear on blacktieguide.com, and avoid the match problem entirely. It's a v. modern-feeling slim-fitting jacket with all the classic details: 1-button, narrow shawl collar, ventless, jetted pockets, and I'm 23, so I might get away with something a little more daring than the standard.
4) along those lines I had a rather left-field suggestion from someone on styleforum.net that I should combine evening- and morning-wear conventions and pair the DJ with grey plaid or pinstriped pants. I happen, though, to have a pair of plaid pants in a bold-checked pearl grey flannel for high-enough contrast, which would be quite an economical solution for me, much as it comes far out of left-field in the propriety stakes. Still, even though they have 2-inch cuffs,the Scotch wear plaid trews with their evening-wear, I suppose...

I'm trying to source a vest for the waist-covering.

The advice on styleforum from mafoofan was that #1 and #2 were not going to look good. Would you agree? what's the alternative?

Thanks.