The patent expired after 15 years and I was not in a position to renew it. I have now found several modifications and materials that were not available to me when I first patented the garment, can I get a provisional patent based on my first patent idea with the new modifications
Yes, you can always get a patent for modification of your invention as long has it improves the functionality of the invention.
For eg your old invention has A,B,C components and you have invented that A,B,D or addition of new component D to exiting A,B,C has superior function then the patent would be granted for the new component D but not for A,B,C. i.e., the patent would be granted for the improvement/modification which you have made, As long as the modification made is not obvious over prior art.
please consult a patent attorney as he would be in a better position to what extent the new improvement can be patented.
While RisheM_IPR's answer if fine, some hints in your question leads me to think there are other aspects to answer.
First, there is no way to "renew" a patent. A patent has a fixed term and so long as you keep up with maintenance fees it stays in effect and then expires. Second, you mention the patent expired after 15 years. This suggests to me that the patent was a design patent and not a utility patent. Design patents have a term of 15 years while utility patents have a term of 20 years. Design patents are fundamentally different from utility patents. They cover the ornamental design of functional objects. Thus they aren't claiming functional features. You don't mention the patent number, but design patents in the US have a "D" in the patent number.
Lastly, while you can file a provisional application, there is no such thing as a provisional patent. A provisional application gets you an early priority date and provides some protection while you draft and file a non-provisional patent application. The provisional application by itself never becomes a patent. Whether or not you can get a patent for the improvements to your design depend, as RishiM_IPR states, on whether the improvements are novel and non-obvious over prior art (which your design patent is part of). There is no way for us to assess this since we would need to know what your improvements are and you can't disclose them publicly. Thus consulting a patent professional is your best next step.