First up I should ask MattKC if I have permission to make this port, and what accreditation I should attach to it supposing I do manage to achieve this.
So out of interest I grabbed the repo, followed the instructions, and tried to put everything together. Suffice to say, it didn't take long to start hitting roadblocks. It wasn't difficult to get the version of Unity sorted, but I had to proxy a ton of commands in NGUI because the animation calls proved to be different from the explicit version that I'd obtained, and it'd turn out that CriWare has been pulled from the Asset Store too. Thus I began proxying the audio calls to see if I could at least get the project to compile. Naturally after finally getting that elusive compile all the GUIDs for assets appeared to have been scrubbed and I was up the creek without a paddle. Thus I'd conclude that I've made a massive mistake somewhere :/
The next hurdle to getting this on the Vita would be actually building to the Vita itself and the only versions available with the necessary SDKs are 2017 and 2018 - there may be SDKs for Unity 4/5 but they don't seem to be widely available - But that's a future me problem, because at the moment it's not even running! lol
Thus I guess this is the part where I ask for help. In an ideal world someone would have a complete zip of this project in a version of Unity equal to or older than 2018 that I could just unzip and get going, the next best would be if the correct versions of CriWare and NGUI just happened to fall off a truck and into my inbox, and I guess the next would be a simple leg up on what I'm doing wrong.
I know I'm probably shouting into the void with this one: a forgotten game on a discarded platform that'll probably only garner the interest of a couple dozen people, but I think that's simply why I love doing this!
Thank you for at least giving this a look over!

EDIT UPDATE:
I stumbled across this fork of the project which requires the server running in the backend to get everything working. It's kind of complete from a gameplay angle (and very broken in some respects) but I suppose it's almost bang on the money for what I was after when it came to a version that'd run on Unity 2018!
https://github.com/maybekoi/Runners/tree/SRU18
Naturally this isn't without it's own set of problems, that being that I'll have to get this working in offline mode, and character setup seems to be broken, as suggested by the constant "Bone weights do not match bones." error message

UPDATE 2:
Definitely need to remove the need for a server backend somehow - it's too much of a dependency for a console that's now in the dustbin, and there is a LOT of server code, enough to make me think that this isn't going to be easy by a long shot :/