Plenty of places to buy braiding, heatshrink and other cable modding materials and tools. Hope it is OK to post these links :-
http://www.e22.biz/Index.aspx
http://www.cablemodders.com/
http://www.shakmods.com/
Cable-Modders stuff is easily found on eBay.
MDPCX although expensive was the ultimate place for this stuff but their promised few month's holiday break has now run to over 6 months.
If you want paracord instead of braiding Amazon and eBay again are good places to look.
Tools for certain types of pin extraction get very poor review from users and DIY solutions are considered as good if not better.
One thing I would suggest is that with braiding you buy the densest weave type you can find. Unless the underlying cable is the same or similar colour to the braid it will modify the hue surprisingly significantly. The denser the weave and the better the braid to cable diameter fit the less the hue will change.
Professional hot knives are expensive and the DIY solutions suggested like using electricians side-cutters then melting the end with a BBQ-Lighter are often unsatisfactory.
Best way I found to cut braid is to use a thin-ish but stiff straight edged kitchen knife heated for 30 - 45 secs seconds over a gas cooker ring (to just off red). On a flat, heat resistent surface (I use a wooden block) very quickly cut/melt though the braid and you'll get a good clean edge with no fly-aways and a very slight lip for the heatshrink, if used, to hold on to.
If there are any fly-aways they're easily melted back by holding the flat side of the still hot knife a few millimetres off but make sure than you don't take too long or the end of the braid sleeving may seal itself together.
For heatshrinking if you have a hot gun then that will be OK but I've had my best, cleanest looking results using a BBQ-Lighter. You can do a much more accurate job in directing the heat and as long as you keep the flame moving neither the braid or underlying cable insulation will scald or melt.
