Do you sell rotor and buckets for 50 ml and 15 ml tubes?

Yes, in each case the rotor is the swing-out rotor for 4 buckets, part number 9238783. For 15 ml conical tubes, catalog number 9020979 is a set of buckets. Each bucket holds 12 tubes. For 50 ml tubes, catalog number 9020901 is a set of buckets. Each bucket holds 7 tubes.