I've had more stress fractures than I can count but never a tibia. What has been okay for metatarsal fractures: stationary bike, no standing, no super-high resistance. The vibration of trainers/spin bikes was bothersome for me until the last couple weeks. The bottom line is you need to ask your doctor.
Get some Twin Labs Tri-Boron Plus and/or Bone Support. An elite running friend told me he uses the Bone Support stuff when he is running lots and/or gets a fracture and he felt it helped them heal faster. I am not sure about healing faster
but they are a good Ca+ supplement, and in my case seemed to help - I suspect I wasn't getting adequate calcium from foods/beverages alone. The tri-boron plus supplement has a bunch of Ca+ in it too. They are superior to other ca supplements - viactiv, for instance, is calcium with a little D and K; these have all the trace minerals needed for building bone.
I looked at the two supplements are they alright to take both together? Found them much cheaper on other sites. Do you take the bone support long term? Or can you just take lower dosages?