For the rears, keep an eye out on eBay (including Ebay.de), or (if the $/£ rate improves sometime) there are clear ones available in the US, where I sourced mine from. The four-spot ones are more expensive, but using a red tint spray on clear rears looks the same - as you can see below:
The amber free ones also come up on here occasionally. Or you can just tint the amber sections red and use green bulbs? I've not seen the results of that approach, but I have heard of it being discussed.
Other way to ditch the rears for clears is to upgrade to the facelift versions - again, there are guides on here and you will also need to look at coding, replacement rear bumper and trim brackets as well.
For the fronts, as
Stuartt points out, donor lights are the only way to find clear hockey sticks these days - there have been a number of discussions around forming replacements, but they've never gone past the "good idea" stage. Alternatives are to use tint spray, mirror foil, or make your own clear hockey sticks from diffuser lights (all have been done on the forum in the past). If you do go the donor light and splitting route, then look for
cj10jeeper's excellent guide
here. If you don't want to split, you can source clear lights from the facelift, or look at aftermarket versions like
these - feedback on these has been mixed, but a number of members have gone down this route.