You can either buy one, have someone send you a level 24 ticket and hope to rip one(or USB save and reload), or you can borrow (and glitch steal it) one
Those, mate, are your options 👍
Welcome at this forum at first. The FGT, as we call it in here, is not a prize car for any race in GT5. That leaves you up to buying it for the 5M in the OCD (Online Car Dealership), or for 4.8 ish in the UCD (Used Car Dealership).
Another option was to trade it, but since update 1.07 if I'm right, it is not possible anymore to gift or trade vehicles worth more than 1M credits. So that option also falls down.
The best thing to do, in my opinion, is to race Seasonal Event races. Those give you quick cash most of the time (most races give around 200K when you win.. You get a 200% bonus when you played GT5 for 6-7 consequentive days, and if you are trying to race with less PP than restriced, you also get bonuses, which will roughly double the prize amount if you have like 30-40PP less than restricted (depends on race, also noted in the description).. That gives you sometimes more than a million per race. I hope this helped you out enough.