Here is a Riccar upright list I found at parts warehouse.com exclusive of specialty models. I saw nothing to indicate the HP Series.
8900, 8905, 8920, 8925, 8955
Brilliance 4 Deluxe, Brilliance 4 Premium, Brilliance 4 Standard, Brilliance 6 Deluxe, Brilliance 6 Premium, Brilliance 6 Standard, Brilliance 6 USA, Brilliance BRLD, Brilliance BRLD.6, Brilliance BRLD.LE, Brilliance BRLD.Retriever, Brilliance BRLD.USA, Brilliance BRLP, Brilliance BRLS, Brilliance Retriever
R100, R10CV, R10CV.2, R10V.4, R10CV.6, R10D, R10E, R10P, R10S, R10SAND, R17
R200, R25D, R25, R25P, R25P Clean Air, R25S Clean Air
R300, R300C, R30D, R30D.4, R30D.6, R30P, R30P.DS, R30PET, R30PET.4
R40, R40.2, R40.LE, R40P.2, R40P.4, R40P.6, R40P.LE
R500, R600, R800, R800C, R800C4
Radiance 10, Radiance 4, Radiance 6, Radiance 6+, Radiance 8, Radiance P2, Radiance P4, Radiance 40P
RSL1 Supralite, RSL1A, RSL1AC, Supralite RSL3, Supralite RSL3C, RSL4, RSL5, RSL5.SAND, RSL5C, Supralite RSL2, Supralite RSL3, Supralite RSL3C, Supralite RSL4, Supralite RSL5C
VIBCBP.1, VIBCNT.X, VIBCL.X, VIBSCLNT.X, VIBD.X, VIBP.X, VIPNT.X, VIBS.X, VIB.USAUS, VIBPBP.2, Vibrance R20D, Vibrance R20P, Vibrance R20P, Vibrance R20S, Vibrance VIBCLNT.X, Vibrance VIBD.X, Vibrance VIBENT, Vibrance VIBENT VIBPNT.X, Vibrance VIBENT VIBS.X, Vibrance VIB USAFS Patriotic, Vibrance VIBC2 Commercial, Vibrance VIBCBP1 Premium Belt Protection, VIBCL USA Classic, VIBCL4 Classic, Vibrance VIBCLNT2 Classic No Tools, Vibrance VIBD2 Deluxe, Vibrance VIBD4, Vibrance VIBDL2 Deluxe, Vibrance VIBE2 Entry, Vibrance VIBENT2 Entry No Tools, Vibrance VIBP2 Premium, Vibrance VIBP4, Vibrance VIBP6 Premium, Vibrance VIBPBP Premium with Belt Protection, Vibrance Vibpnt2 Premium No Tools, Vibrance VIBPNT4, Vibrance VIBS2 Standard, Vibrance VIBS4, Vibrance VIBST2 Standard, Vibrance VIBUSA.SU Patriotic