Don't be hopeful about this, you probably get better 'results' from gambling deposit promos than an exchange deposit bonus.
That is a better alternative if you cant find any exchange that give bonus then you can find many other gambling sites that have this.
I think op is looking for exchanges that offer free bonuses, to add them to his website (probably) mentioned in his signature. The website named GetPaid shows a selection of how to earn money for free or for simple tasks [including surveys and faucets...] So he will not get interested in gambling platforms.
From what i can remember, coinbase offers signup bonus and i can't remember if blockchain.com still offer free xlm for verified users.
OP,
In this
thread, there is some methods about how to earn cryptocurrencies without invest or purchase, you may find some good suggestions to add in your website .
Good luck .