Oil Filler Cap for 1600cc GTi (1980 W Reg)

I've done it before but this time I wasn't so lucky !
I left my Oil Filler Cap on the battery as I filled the oil.
I put the oil away in the garage and then closed the bonnet.
A couple of days later and I'm standing by the car wondering why there's steam/smoke coming out of the bonnet.
I open the bonnet and notice the missing filler cap and neat sprinklings of oil all over the engine.
Anyway I'm a MUPPET and I'd like to get hold of a new Oil Filler Cap.
Local garage seems mystified as to what I need and point me at other garages. Reading up on the net a new cap that will fit is easy to find - but I guess it'll be plastic. Can anyone point me in the direction of a new oil filler cap like the old metal one ?
Thanks for your help.

It's worth 5 minutes examining the really dark nooks and crannies in the engine bay before you give up hope completely…

I thought I'd lost my header tank cap, but I found it months later in between the inner arch and the bulkhead.

If you have no luck talk to Crazyquiff or Scouse on here.

HTH

Rich

Thanks for the info - I'll go have a look with a torch once the rain has stopped.

Euro Car Parts do plastic replacement ones - seem fine to me.

Cheers