I want to purchase a long put on spy 40% otm for tail risk hedge 1 year to exp and my portfolio only has $5k in capital.

The rest of my portfolio I want to hold the BND etf.
How would I variably allocate enough capital to purchase the contract, of contracts can very in price depending on markets volatility.

I don’t want to set a hard allocation percentage of my portfolio to contracts like set.holdings(contract, .1) because what if the contract costs more than 10% of my portfolio's capital?

Instead, I want to do something like
Total Capital-contract price= allocation for bonds
Total Capital - contract price = allocation for contract purchase 

So that way if I want to purchase a contract once a year, I'll be able to regardless of my total portfolios capital (assuming I have at least enough to buy one long contract)


Thank you!