How to take a sample of a hot salt solution without it precipitating in the cooler glassware due to the difference in solubilities at different temps?
Just use your room temperature volumetric pipette, and wash out the precipitate with water. The exact density at 85°C is going to be tricky anyway. The expansion coefficient of borosilicate you can find, and you need to measure or calculate (heat capacity of borosilicate, and your solution?!? IR thermometer?) the temperature of the solution.

You might think about using a second volumitric pipette with dest water, and wash everything into a beaker with known empty weight. 

Have fun with calculating the uncertainties! ;-)

Afterthought:
Fill the RT volumetric pipette from the hot solution. Wait until cooling (the filling should get lower, because water has a larger expansion coeff. than glass) and precipitation is complete. Now completely fill the pipette, the additional amount of solution will be rather small, and you don't need to wait again for quillibration.

Now weigh and titrate the solution&amp;precipitate (after washing out with a known volume of water). You know the density and molarity of cold strontium hydroxide solution, you know the density of solid hydroxide. I think that is sufficient information to calculate the concentration at 85°C.