This is an old list from when this was a hot period for me (not sure how many are still available):
Wargaming Figures (originally by Hal Thinglum, updated by Darryl R. Smith)
Brigade Games has a new line of 28mm Marines, Haitians, Sandinistas, and South American Javaros in their Caribbean Empires range.
brigadegames.com
35 Brookvale Road
Kinnelon, NJ 07405
Cannon Fodder Miniatures (what a GREAT name!) has a very nice line of 28mm Marines and sailors in their Yangpat range.
canfodmins.com
P.O. Box 786, Bendigo, 3552
Victoria, Australia
Falcon Miniatures have a 25mm Marine and a Marine officer for the 1900 period.
falconminiatures.net
5 Hampshire Road
Peabody, MA 01960
Frontier Miniatures has (had) a very extensive line of 25mm figures for the Boxer Rebellion (1900), Spanish-American War (1898), Veracruz (1912), Pershing's Expeditionary Force (1916-1917), Moros-Filipinos, and China (1920); and 15mm figures for the Boxer Rebellion and Spanish-American War. Acquired by The Tactical Edge, however recent attempts to contact them have been for naught.
90 Spirit Lake Rd.
Winter Haven, FL 33880
Homegrown Miniatures has a recent line of figures for this period. Currently they offer Marines and Sandinistas in 28mm along with buildings.
link
1252 Center Avenue
Tarpon Springs, FL 34689
Tiger Miniatures (formally the Honourable Lead Boiler Suit Company line) has an expanding line of Spanish-American figures in 28mm that includes Cuban insurgents and U.S. Marines. Pick them up from The Heliograph.
Lyzard's Grin has some 25mm equipment in the line of guns, etc. that may be appropriate. Now made by The London War Room.
thelondonwarroom.com
41 Beverly Hills Loop
Petal, MS 39465
Monday Knight Productions have taken over the Pass of the North 25mm Banana Wars line (U.S. infantry and cavalry, Moros, and Haitians).
mondayknight.com
534 SE Oak Street
Portland, Oregon 97214
Old Glory has a line of Boxer Rebellion figures which includes U.S. Marines, as well as a line of Spanish-American War figures that include Moros. Both are in 28mm and carried by Grandiosity.
warweb.com
P.O. Box 750992
Dayton, OH 45475
Pulp Figures make some nicely done Marines and sailors in 28mm.
pulpfigures.com
P.O. Box 29063
Okanagan Mission R.P.O.
Kelowna, BC, Canada
V1W 4A7
Redoubt Enterprises make 28mm Marines in their Boxer Rebellion range of figures.
reboubtenterprises.com
Unit 2, Glennys Industrial Estate
158 Latimer Road, Eastbourne
East Sussex, Great Britain
BN22 7ET