Congratulations, sounds like an interesting new job! I'm not in the same field but I switched jobs last fall to a small 5-person company, also without a 401k. I'd brought up the idea of a 401k plan to my boss several times, and it finally clicked with him when we were attempting to hire a new associate and candidates were concerned about the lack of a 401k. We now have a SIMPLE IRA set up, with a 3% match. Max is only $12,500 compared to the usual 401k level, but I'm ok with it for now. It's better than nothing! 401k plans can be expensive for small companies.
Basically, if you think you'll enjoy the job, I'd say go for it! It's probably best to inquire about a 401k or SIMPLE IRA before accepting the job, to see if they'd be willing to work on something to help bring you on, but you could also take the chance and wait until you start working. After you've been there for a few months and things are going well, consider presenting a plan to the owner/management of the company. Explain that this would be a huge benefit to current employees and an attractive feature to future job candidates, even if it's just access to the plan (if your company doesn't want to do any matching). Lay out how much it would cost, how employees will contribute, etc. to help in their decision and show you've thought it through.
Again, congrats on the job offer and I hope all goes well for you! Best of luck.