It's a financial commitment, but less so if you keep the hair short and get a long lasting system like poly plus if the hair is short and you are put in a situation you can't get a system you can just shave it and restart without having to wait too long to get back where you want. Right now is a tough time though as well with supply chains being messed up and systems taking a long time to be made so you may want to wait before even messing with systems.
Without even doing anything though if it's just one small spot using conditioner can really help a thicker hair look, I didn't really think much about conditioner when I was younger since my hair was short and wasn't as thin and guys aren't always the most caring about their hair until they need to be. I was out of conditioner yesterday and my hair looked so thin, I forgot how thin it looked because when I condition it I get pretty good coverage, but without conditioner it looked pretty bad lol. Maybe you've always shampooed and conditioned though and this part is irrelevant, but just throwing that out there.
Without even doing anything though if it's just one small spot using conditioner can really help a thicker hair look, I didn't really think much about conditioner when I was younger since my hair was short and wasn't as thin and guys aren't always the most caring about their hair until they need to be. I was out of conditioner yesterday and my hair looked so thin, I forgot how thin it looked because when I condition it I get pretty good coverage, but without conditioner it looked pretty bad lol. Maybe you've always shampooed and conditioned though and this part is irrelevant, but just throwing that out there.