Thinking about building a portable toolbox for fletching and other arrow maintenance. Similar to a fly tying setup where the jig can be secured on the outside of box.  Has anyone seen anything fitting this description?

No, but sounds like a good idea.

I have my fly tying portable for "match the hatch"
but usually a partly used tube of nock glue and slow gel super glue, a couple nocks, a Whiffen taper tool and a good knife will fit in my day pack and will fix minor tip or nock breaks.  Take enough arrows in your quiver to do the day, and in a box for the trip at camp.  I would leave the major repairs for back home.

The box would be for home and travel.  Small house and two young boys means daddies tools need to be put away when not in use.  I am hoping to fit 2-3 Jo Jans.

I use a fishing tackle box for just the thing you are talking about. I have a Jo Jan Mono fletcher and a couple clamps in the bottom of the box along woth feathers, knock plyers, inserts. hot glue, fiels points, knocks, string wax....etc....etc...

2x the tackle box

I always pack an emergency kit when going on a "hunting road trip".  My kit is in a small tackle box and contains the following: A fletching jig, fletch glue, hot melt, a lighter, a razor blade, some spare nocks, some serving, a brass nock pliers, some brass pinch-on nocks a T-square and some string wax.

Another tackle box user here.

fletch tape and some glue....saved my bacon on a caribou hunt last fall when my original duco failed....tape held things in place while the glue dried....ended up having to refletch when I got home.   I do carry some points and nocks....just depends on the hunt.   A jig is nice to have but not something I can regularly travel with.

I used to use a large tackle box and drilled 2 holes in the base of a Bitz and screwed it to the lid of the box. Worked like a charm for years. Do many arrows for it now though.

I have a little one, I keep in my truck.  I take about 6 feathers, use the fletch tape on it so they are ready, and few pins.  Also little glue and nocks with sharpener.