Working in an isolated environment
I was in a pretty similar situation, so I can sympathize. Although, personally I found it less critical for me to have these interactions. Don't get me wrong - it was not easy to work this way, but I saw it as an opportunity/challenge to develop my independence as a researcher.

However, I was able to get some ideas and interactions in the following ways:


Presenting my work at various forums - any size, from group/lab meetings to seminars and conferences.
By establishing a collaboration/semi-collaboration with relevant people at a different institution.
In terms of ideas - sometimes just reading a lot of literature helped (but this can be field-dependent).
By interacting with the "mathematically unskilled" people at my lab - might sound surprising, but sometimes you just need someone to interact with and ask basic questions even if they are not knowledgeable.


Personally I also found that I don't need these interactions to be very frequent, sometimes it is enough to interact, get a seed of an idea, and then go work on it for a month on my own.

Good luck, for me it worked out very well in the end and I can say I developed significantly as a scientist, and both sides benefited.

One more piece of advice - while you are dealing with the math, don't forget to keep in close contact with the experimentalists so you don't drift away trying to solve some problem which is not relevant.