Renthal sprocket for ZX10R is 289-525-17, so any sprocket using 289-525 numbering will fit. Here is a list of the bikes using these front sprockets, you may be able to find an 18 tooth sprocket for one of these.
KAWASAKI
KLV1000 04-05 (A2H)
W650 99-00 (A1), 2001 (C3), 01-02 (C4), 02-04 (C5), 2004 (C6P), 2005 (C7P)
Zephyr 750 1991 (C1), 91-93 (C2), 93-94 (C3)
ZR-7 99-00 (F1), 01-02 (F3), 02-04 (F5)
ZR-7 S 01-02 (H1), 02-04 (H3)
ZX-10R Ninja 04-05 (C1H), 04-05 (C2H), 2006 (D6F), 06-07 (D7F), 07-08 (E8F), 08-10 (E9F), 2010 (FAF), 11-12 (JBF), 12-13 (JCF)
ZX-7R Ninja 1996 (P1), 96-97 (P2), 1998 (P3), 98-99 (P4), 99-00 (P5), 2001 (P6), 02-03 (P7)
ZX-7RR Ninja 96-99 (N1)
SUZUKI
DL1000 V-Strom 02-03 (K2), 03-04 (K3), 2005 (K5), 05-06 (K6), 2007 (K7), 08-09 (K8)
DL650 V-Strom 2004 (K4), 04-05 (K5), 05-06 (K6)
DL650 X V-Strom 07-08 (K7), 08-09 (K9), 09-11 (L0), 2011 (L1)
GSF650 Bandit 2007 (K7), 07-08 (K8), 2009 (K9), 10-11 (L0)
GSF650 S Bandit 2005 (K5)
GSF650 SA Bandit 2009 (K9), 10-11 (L0)
GSR600 06-07 (K6), 07-08 (K7), 08-09 (K8), 2009 (K9)
GSR750 11-13 (L1), 12-13 (L2), 2013 (L3)
GSX-R600 00-01 (K1), 01-02 (K2), 02-04 (K3), 2004 (K4), 04-05 (K5), 06-08 (K7), 08-09 (K8), 09-10 (K9), 10-11 (L0), 11-13 (L1), 96-97 (V), 97-98 (W), 99-00 (X), 2000 (Y)
GSX-R750 2001 (K1), 01-02 (K2), 02-04 (K3), 04-06 (K5), 2006 (K6), 06-08 (K7), 08-09 (K8), 09-10 (K9), 10-11 (L0), 11-13 (L1), 2013 (L3), 97-98 (W), 98-00 (X), 2000 (Y)
GSX650 F 08-09 (K8), 2009 (K9), 10-11 (L0), 11-13 (L1), 12-13 (L2)
SV650 00-01 (K1), 01-03 (K2), 03-04 (K3), 2004 (K4), 2005 (K5), 05-07 (K6), 2007 (K7), 2008 (K8), 1999 (X), 99-00 (Y)
SV650 S 00-01 (K1), 01-03 (K2), 03-04 (K3), 2004 (K4), 2005 (K5), 05-06 (K6), 06-07 (K7), 1999 (X), 99-00 (Y)
SV650 S Sport 2008 (K8)
TRIUMPH
Daytona 675 06-09, 09-11, 2013
Daytona 675 R 11-12, 2013
Street Triple 07-08, 09-12, 2013
Street Triple R 08-12, 2013
Tiger 800 10-13
Tiger 800XC 10-13
YAMAHA
FZR400 Genesis 86-87
TDM850 1991, 92-93, 1993, 94-95