Maybe do what I do if you are not too worried about appearances - only function. Buy a metal hood for longer focal lengths in a diameter of say 43mm (I find that 43mm is a pretty good option but you can also use 46mm - much bigger tends to block the finder too much which is why I prefer 43mm). The hood I am thinking of is of tubular shape with no venting. Like this https://www.ebay.com/itm/43-mm-Metal...UAAOSwnNBXaPMg
Get a 39mm-43mm stepping ring and use this paired with the hood. Total cost less than $10. It works perfectly well and in the mean time you can look for something more stylish if you wish.
I have an old hood labelled Canon "for EEE" 42mm c which fits well and is presently mounted on my thin Tele Elmarit which has a 39mm filter thread. The hood is clamp fit.
it is the same as this one: https://kamerastore.com/product/cano...BoCkTEQAvD_BwE
Also shown here - with a picture of the hood plus the gizmo it was designed to fit:
I also have a hood that fits 43mm which was originally for a Ricoh lens ( no idea which but the hood is so labelled) and have seen suitable 43mm hoods turn up now and then for other old lenses too but they are even more rare than the Leica ones. but if you stumble on one, with adapter ring to 39mm these work well too.