you can buy new one from felindre servicing in wales who are the official shimano distributer and service agent , for £40 EACH
IF YOU CAN FIND THEM SECONDHAND THEY MAKE AROUND THE SAME MONEY
only the longcast , aero tech 10k and the very early power aero spools will fit , the later biomaster , technium and ultegra spools all ues the same blank but the top seal assy is totally diff and does not fit .
I had some original tech 10k that had been converted to 12k xta spec with baitrunner caps and it cost me a fortune and a load of hassle finding out what fits what to convert back