I went down this rabbit hole when I brought my RHD Touring over to the US.
You can't put (install) a sealed beam headlight into a Euro style bucket.
For LHD cars, BMW had both Hella & Bosch supply the headlamps, but, you couldn't swap the reflectors from one to the other as the adjustment parts were different. Also, for LHD you had the choice of H4 or bilux, and, again parts were different between Hella & Bosch.
So, any road up, for RHD (if you can believe the BMW Blue parts book) only Hella supplied the headlamps, and only one type (Bilux). The Bilux bulbs were held in by a complicated spring loaded socket that you pushed onto the reflector and turned a little to the right to lock it on under three small tabs on the reflector (see the reflector on the right in the pic below). The H4 type was easier as there was a spring clip that pivoted over and latched in on the reflector (see the two on the left in the pic below).
In theory, you need reflector part # 63 12 8 650 120 which I believe is NLA. However, Linwar in the UK, did have complete headlamps for RHD but be prepared to spend a lot of coin.
https://www.linwar.com/e10_163_12005_00.html
I don't know what (& why) the difference between a RHD reflector & a LHD (other than differing BMW part nos). I just thought it was the headlamp glass that differed in order not to blind oncoming traffic. However, if LHD reflectors are available & you want to try that route, you'll need to ensure you can get one matches the adjustment mechanism in your buckets, if not, it's the Linwar option, or maybe you can get your reflectors re-chromed????.
FYI - Walloth & Nesch sell the H4 bulbs that will fit in the Bilux reflectors.