There are a bunch of issues here. The little triangular piece that screws down over the toe clip comes in three varieties, two for steel clips (an early one with room for very thin tabs on the PD-64 cleats, and a later one with more room for thicker tabs so the PD-64 cleats wouldn't break as frequently) and one for plastic toe clips. They will all mount in the same holes, but you need the right one for the clip and the right one for the cleats if you plan to use the matching cleats. All these little parts are pretty much unavailable. The screws have to be longer for plastic cleats and are a nonstandard design so they sit flush, so you need the Shimano screws. Get the picture?
Shimano packed pedals with one pair of Large steel cleats, which were more like a Medium in a Christophe or MKS or other toe clip. They weren't very good at supplying spares. There was also an aluminum one briefly, but they broke very easily and they were only available aftermarket (never with the pedals).
All that said, many people tended to dump or give away the Large clips to get ones big enough for their feet ("Large" was for Japanese audiences) and in the end there was a small availability in Large and slightly more in Mediums, but those are all gone. Except in complete pedal kits, they are pretty much unobtainable and there's no alternative.
If you like that look in a pedal, check out the Campy pedals of the same vintage. They look similar but have a small front plate that is just enough to mount a standard toe clip.
On the track sprinters still use these pedals without the toe clips because the clip is really only there to support the strap when you flip your foot in on the road. But even there, choices have tended to move on to pedals with actual availability of parts.