I lived in a small town called Roscoe right on the Wisconsin/Illinois border just north of Rockford for 30 yrs, before moving down to Florida in 2007.
Yea guilty I'm an Engineer. I own my own Industrial Design company (my day job), basically I sit in my pool all day designing/inventing stuff. Sailing and playing around with my Hobie, and Scuba diving is my hobby and exercise program on the weekends. My sailing hobby has nothing to do with the next generation laptops/servers, next generation explosive oil field perforation systems, figuring out how to take a skin cell and turn it into an ear, and nothing to do with the next generation DNA sequencing systems, electronic heart monitors, or blood bypass systems, and especially nothing to do with the current MIRV systems (thus the name Fusioneng, not too proud of that one LOL). All current projects that I don't even want to think about when I'm out on the water.
I don't think it's a straight line from the front AKA thru the rear bow sprit brace, and then up to the tip of the bow, so a one piece solution might be difficult. The front short sections (on the outsides) don't have to be that rectangular tubing, you could get by with 1/8 x 3/4 flat aluminum (you may need to twist/bend it slightly), it might end up a little easier and cheaper to build using flat stock.
Of course you could eliminate that back brace piece of the bow sprit altogether if you like (might make it easier to make). CaptnChaos's design and Hobie's design with their original bow brace design for the TI (used in the 2011 EC challenge race by Hobies Chief Engineer) both just had just two pieces of rectangular tubing going all the way to the bow, screwed down to a plate on the tip of the bow, thus eliminating that whole back brace thing I did in my design (probably simpler in the long run). My only reason for designing a complete truss structure was to spread out the stress upon the entire bow to a larger area, and allow attachment without attaching to the lifting lug in any way, It's probably over designed but nobody had done anything like it before, so I designed it easy for me to make in my garage in a weekend with materials I had on hand in the garage at the time ( ie... the 3ft pultrusion, and the aluminum stock I had on hand). I only made the thing to try it out quickly to see if it worked, then planned to design something later that was engineered properly, more substantial and correct later on. To my complete surprise it worked great and has held up all this time with no issues (way over 5000 hard sailing miles to date) "Who knew" LOL. Same with the Roto furling mast topper, it's was just something I threw together in an afternoon with stuff I had laying around just to try out, again 'who knew' it was going to work so well and last so long with no issues at all. I'm still running all the same stuff, with just a couple small minor improvements, and am out every weekend just sailing and enjoying my hobby. Really no need to over think it, just build it, I'm sure whatever you build will work just fine.
I just get stainless steel screws nuts and bolts from either Lowes or Home depot.
Hope this helps