Kudos to you on jumping in and actually starting your start-up! And congratulation on your initial success (finding a market and making sales).

It sounds like you've hit a proverbial wall... In that your original business model is maxed out.

If that's the case - This is point where you need to pivot. (In other words - you may not need a new business model.)

However, without knowing more about your current business model and the details of your business (including whether you are profitable or not, what your margins are, what your current capacity for production is, resources, etc) it's impossible to help with a business model that has any reasonable chance of success.

Any suggestions you receive without more data would be literally blind guesses... Not the kind I'd invest in.

I'd highly suggest you seek the assistance of a business coach (or find an experienced entrepreneur to partner with).

I wish you the best of luck in your future success!