I don't know what the rest of your financial picture looks like, but you could possibly consider Asset-Based Lending. It's essentially the same thing as a HELOC, but uses the assets in your brokerage account as collateral instead of a home.
Some points to note:
These types of loans are only available in managed brokerage accounts, so if your stocks/bonds/ETFs are in an eTrade account (or whatever), you'd need to move them first.
These accounts typically require something like a $100k to $125k minimum asset value to approve a loan, so if you've got less than that it wont work.
Most managed accounts cost a 1% annual management fee, so think of that as an extra 1% on top of the interest rate.
These accounts typically let you borrow up to 75% of your equity, but due to market fluctuations, you should consider imposing your own, smaller limit.
Interest rates are comparable to a HELOC, plus that extra 1% management fee, and like a HELOC, it's a revolving line of credit vs a fixed, monthly payment. You only pay interest when you borrow against it and while there is an outstanding balance.
I have someone I can recommend, if you want to discuss with a professional. DM me, and I can share his contact info.