The 4 fuse box is not standard equipment on any Dolomite (they only ever had 2 fuses from the factory)
This 4 fuse box is used on the MKIII Spitfire and also (IIRC) on MGBs and probably several other cars too. So it'd probably aid your search to put these models in your ebay specs. Or just put in "Lucas 4 fuse fusebox" THough i'm pretty sure the lid was never sold separately, so you may have to buy the whole thing!
Steve
'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!
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Steve is quite right in that the 4-fuse box was never fitted as standard to any Dolomite.
However I do have one on my MGB.
If yours is the same, the 4-fuse box is part no 37H4727 and the cover is item 32 which is 37H4727A.
It may be a question of ringing around the MGB suppliers and seeing what they have.
Good Luck with it ,
Tony.