If you have Caterpillar D2 track frames, I do not believe there are any aftermarket suppliers of those parts, S.A.L.T. or what came on those tractors. CAT does not offer any, you could do some research to see if Berco or similar offers any sealed chain for those track frames.
It would appear that perhaps you may have to convert those track frames to D3 undercarriage, which may be available in S.A.L.T. There is some work involved with doing that, someone on ACMOC or ACME antique caterpillar forums may be of better help than I, would not hurt to ask over there as to what options you may have with this.