I got mine from ebay, had to bid to like £320, not bad considering it's worth around £400 from seibon and just sold my original bonnet to someone on here for £100. My cars at kwit fit, hope they haven't taken if off and selling it on ebay lol. The last time i looked theres only a few company that does carbon fibre bonnets for lexus, but i could be wrong, the better ones seems to be:-
Carbon CultureSeibonOther makes may not have the UV light coating and will fade to gray after a while.
Maybe worth contacting Prolex UK, or if you join us as gold member, you can post in the "wanted" section and someone might have a second hand one for sale (very rarely). But yes it's expensive, but it's carbon fibre.
Oh and welcome to LOC!