What flies are you planning to throw? Big water, small water?
I fish small eastern water with small flies (little unweighted streamers, wets, etc.) by using a line at the rod's rating, or uplining 1-2 line sizes on my short glass 3, 4, & 5 weight rods. You can haul just like overhead casting for carrying slightly larger flies or to carry more line. This works well for me with WF/DT floaters and WF intermediate lines. You may already own a line that will work for you. You will have to play with different lines and leader lengths to find your happy spot. Just because a given line isn't labelled as a "spey" line does not mean it can't be spey cast. Doing this will NOT replicate the shooting head casting experience, it will reasonably replicate the traditional (fixed length of line) spey experience though. If there's a chance of dry fly fishing, this way works nice as all I have to do is change a leader and a fly, no extra spools, heads, tips etc to carry.
Again for smaller water, if I want to throw bigger flies, fish polyleaders for some additional depth, or need some (not major) distance, OPST Commando Heads get it done for my short glass rods.
On bigger water with my trout spey outfit I use longer heads... Rio
Trout Spey or Rio
Scandi Short depending on water level and fly size.
Your 10' 4wt should be able to do just fine with a shooting head or uplined standard single hand line depending upon your application.
I don't have a euro-nymphing rod, but other members here may. If you could state the particular rod you're using, it may help you get some specific line or head weight recommendations. Someone out there has your rod and has already done this.