If you are in the USA, don't waste money on crap seed imported from sketchy Chinese Ebay sellers. There are quite a number of reliable seed suppliers that have real world, brick and mortar companies in North America. Ebay sellers of seed often purchase out of date, expired seed from more reputable companies, or they just pack "any old seed" into envelopes and ship it know by the time the buyer figures out they were victims of petty fraud, they will be long gone, money moved and no way for you to lodge a complaint or get your money back.
Besides, seed is the "slow route" for bonsai. Google California Bonsai Suppliers. European olive trees, dug up from California olive groves are a staple of California bonsai. You can get 40, 50 or even 100 year old stumps of olive trees from California bonsai suppliers if you are interested.
For reliable seed companies I have had excellent experience with:
Sheffields Seed Company offers 1000s of quality seed for sale varieties with fast worldwide shipping Phone 315 4971058 Fax 315 4971059 Email seedsheffields.com
sheffields.com
International Tree Seed Horticulturist Company since 1926. Tree seeds and shrub seeds for sale from around the world. We import and export a variety of seeds. Give us a call or send an email.
www.treeshrubseeds.com
Offering rare and heirloom seeds perfect for any climate. Over 1500 varieties of peppers, tomatoes, vegetables, heirlooms, tropical fruits and ornamentals.
www.tradewindsfruit.com
You are in Colorado, there are excellent opportunities to hike out into the mountains and collect your own trees. A number of Colorado natives make excellent bonsai, including Ponderosa pine, Limber pine, Pinion pine, Rocky Mountain Juniper, Any of the spruces, and many, many others. Look into joining the Denver Bonsai Society, even if too far away to attend in person, they are a good clearinghouse of Colorado orientated information.