Google search will bring up thousands of this kind of sites to chose. With the keyword sportsbook api providers I got following results on the first page.

https://rapidapi.com/collection/sports-odds-betting-apis
https://nuxgame.com/solutions/seamless-wallet-api
https://oddsmatrix.com/
https://www.gammastack.com/sports-betting-3rd-party-api-integrations/
https://www.programmableweb.com/news/10-most-popular-gambling-apis/brief/2019/11/29
https://www.lsports.eu/oddservice/
https://www.orioninfosolutions.com/blog/best-sports-betting-api-provider-in-india
https://uplatform.com/news/choosing-a-sportsbook-api-why-and-which
https://www.webodoctor.com/blog/take-a-glimpse-on-the-best-sports-betting-api-providers-in-india

I am not endorsing anyone but it's easy to find and research. OP can do his own search on the web.

I think to find the API for sports events and bookmakers some praise the iSports API as it covers the full range of sports data in more than 900 different international and national competitions, cups and leagues in all major football federations around the world. There are also free APIs from Betfair, Matchbook and Pinnacle that allow you to provide odds and place bets.

This is something only those who own sportsbook, sportsbook directory or anything that relates in monitoring and using sports booking services can only answer. Simple words, business owners as this api probably have charges monthly, fix, or whatever.
I hope you can get a detailed or expected answers.