iodinedownload the hud, get the crosshair vmt and vtf from the hud, and then use those files to make a vtf crosshair.
to give some further info:
VTF is the crosshair image
VMT is a small text file so the game knows some properties the VTF will use
If you are unfamiliar with VTFs, here's probably the easiest way to do it that requires the least understanding of what you're doing (you don't need delfy's VMT file for this, just the VTF):
https://cfg.tf/tools/crosshairs/ go here
make a crosshair pack, all with the same crosshair on every weapon (example: crosshair1)
You have to go through the entire list manually for each weapon, like 3 minutes of work but tedious nonetheless
Once you have crosshair1 on each weapon, download the package and extract the main folder
put the folder in custom and open it. You'll see Materials, Scripts and Sound.
Open Materials > vgui > replay > thumbnails
There'll be a list of VTF and VMT files, find crosshair1.vtf (or whatever crosshair you chose on cfg.tf)
Now remove crosshair1.vtf and instead put in delfy.vtf or whatever it is called
Now rename delfy.vtf to crosshair1.vtf
Open TF2, use the command cl_crosshair_file "" (double quotation marks, no space between)
Alternatively you can go to Options > Multiplayer and select the None crosshair
If you've done the steps correctly you'll now have Delfy's crosshair.
As far as getting the delfy's VTF file from the hud you're on your own, but if you have trouble with finding it send me a PM.
If you're at the final step but the crosshair is a purple checkers error texture you messed up a step. There probably is no crosshair1.vtf in the thumbnails folder
If you're at the final step and some weapons have the crosshair, but others don't, you probably missed a couple weapon files on cfg.tf when you were making the package
All in all you're just putting a folder in custom, removing one file and renaming a file so the individual steps aren't hard. Just a tedious process if you've never done it before