329 Clover Stitch Ring Markers have 10 small markers and 20 large markers in pink and blue, made from ABS resin. Fits up to size US 13 (9mm) needle.
354 Clover Jumbo Stitch Ring Markers have two sizes: 10 smaller rings fit up to a US 15 (10mm) needle and 10 larger rings fit up to a US 35 (20mm) needle.
3107 Clover Soft Stitch Ring Markers have 10 small markers and 20 larger markers in green and purple. Made from a flexible material and fits up to US 11 (8mm) needle.
Knitter's Pride Amour Stitch Markers are coated metal markers in two shades of pink hearts! A total of 40 markers. Fits up to a size US 9 (5.5mm) needle.
Knitter's Pride Linea Stitch Markers are coated metal markers in purple, yellow, blue and green. There are 10 each of small round and square; 10 each of large round and square for a total of 40 markers. Fits up to a size US 15 (10mm) needle.
Knitter's Pride Stitch Ring Markers are green and purple in a range of sizes that will fit up to a US 35 (20mm) needle. Approximately 50 markers.
Susan Bates' Wafer-Thin Stitch Count Markers are really thin, rigid plastic red and blue markers. Fits sizes up to US 15 (10mm). Approximately 20 markers.
Cocoknits' Markers - and their other accessories - can be found here.
Also, Pewter Stitch Markers designed by a Maine Knitwear designer can be found here.