Recommendations for the best cold email agency for bootstrapped companies?

We don't have a massive budget, but we need leads to survive the quarter. I’m trying to find the best cold email agency that offers a fair pricing model for startups. A lot of the big players want $4k+ per month which is totally out of reach for us right now. Is there a middle ground where you get high-quality data and deliverability expertise without the enterprise price tag? I'm looking for a partner who is willing to iterate on the messaging based on the feedback we get from the first few campaigns.