Many fonts on Typekit support Czech. You can browse fonts that support Czech by selecting "Czech" from the list of supported languages in the sidebar under browse fonts.
After you have added a font to your kit, choose the "All Characters" option or create a custom language subset which includes Czech to add the language to your kit. Republish your kit, and the Czech characters will be available to your website within a few minutes.
The Language Support & Subsetting help page has more information on the character set options.
All fonts that support Czech include the following letter characters, at minimum: