Bolt Man

Hey all. I recently got myself a nice IS200 (2001) so decided to join the forum. I don't know a lot about cars (I've only done basic jobs) but I've always thought these were cool looking! The car I bought has a Jap Speed Cat Back system on it and I love it 🙂 Thing is, I need to put a stock exhaust back on for a while for insurance purposes, then the cool exhaust can go back on 😛 So, I bought myself a new, stock mid section & back box, a fitting kit which consists of a gasket with two nuts & bolts, and a conical gasket. I also have some exhaust putty. I've got someone who knows what they're doing to help me fit the exhaust so I'm all good for that. However, they said I might need to buy the spring loaded bolts that connect the back box and mid section together. Even if the right ones are currently on the car and I can reuse them, I'd rather just buy some new ones anyway seeing as the rest is being replaced. The thing is, I don't know what the hell I'm looking for online - I have no idea what the name for these spring loaded bolts are. I've been searching around and I just never see them. Can anyone tell me what to search for or maybe link me to some on an online shop? Thanks!