Try the article in the grey Mag 2024A about LED lights - there are links to various suppliers of bulb holders. In your case, you might want to use a double-pin type and fit these bulbs that do not need a reflector in good condition:
https://www.classiccarleds.co.uk/product...nd-pattern
Bulbs Holders of various kinds:
This should show a wide range:
https://www.autoelectricsupplies.co.uk/c/bulb-holders
https://www.classiccarleds.co.uk/product...-sidelight
https://www.autoelectricsupplies.co.uk/p...ulb-holder
https://www.classiccarleds.co.uk/product...everse-382
https://www.classiccarleds.co.uk/product...-sidelight
Or, how about these - I've no experience of them and they appear to be a new addition to the Company's stock.
https://www.autoelectricsupplies.co.uk/p...lb-holders
How is the new holder fitted? In one case the writer managed to bend back the metal tabs holding the ceramic contact unit, remove it and just assemble it into the existing holder. If this is not possible, the original holder will have to be sawn off and the hole enlarged to fit the new. Cutting off the old one with a Junior hacksaw is easy, but how to enlarge to the hole to the 17 mm diameter of the new holder? The writer managed this by using, with great care, an adjustable reamer and taking very small cuts until the new holder was a snug, push-fit.
Next, how to retain the holder: solder can be used, though this can be tricky and a far easier way (and with which the writer had success) is to use Araldite or a similar two-pack adhesive. If everything is cleaned thoroughly - finishing with alcohol - the job will be successful. Before getting the glue ready, remember that the bulls-eye bulbs need to be fitted so that the black line on their body is exactly at the top. With the Araldite still flexible, the holder can be positioned but, if your reflector is the push-in-and-twist type (like an R47) you’ll need to install it and make a mark showing its top. Next, with the bulb fitted into its holder, position it so that the black line is at the top and mark this on the holder. With the glue still not set, the two marks can then be aligned—but, if the positioning is found to be slightly out, the bulbs can still be adjusted - there's a small hex-head screw that allows the body to be twisted a little for final adjustment.