I believe there is a product like a colored (matched to a particular
shade you might need) silicone-type grout. I was unable to drill
under my fireplace bricks when I did my laminate floor (6 months ago)
so I've got a quarter inch gap here and would like to fill it with
some grout type stuff that will give (in case the floor moves). Where
might I find this locally? Home Depot or Lowe's? If not, any ideas
where I might find it online?

Thanks,
Matt