You would need to provide a data sheet for the 8mm version then (and from the looks of the google search i did there may not be one.) The barrel of that LED is in fact 8mm as well (as specified in the listed data sheet.)
edit:
It is possible (just not easy) for you to modify the part. These two tutorials provide instructions:
I lately learned there aren’t links to the videos in Old_Grey’s tutorial so you need to do a google search for the title and then they come up on YouTube.
My opinion is and always has been that for a small number of parts you are better off to leave making the part to someone experienced because learning to make or modify parts is complex. In this case, assuming you can’t find a data sheet (and as noted I think that is unlikely because nothing is showing up in a google search) an explanation of what is different from the current part to whatever it is you want may be enough. Are the leads not 1.27mm pitch for instance?
As noted the current part appears to be an 8mm LED, it however may well be different than whatever you have.
A google search for “DC5V WS2812D F5 F8 8mm Round RGB LED WS2812 chipset inside RGB Full color Frosted LED Chips” from the website you posted provides this new data sheet which does have pin sizes (but is also apparently identical to the posted part!)
so an explanation of what is different about whatever you have may be all that is required.
Peter