Not sure, but if you find clear ones and prefer them smoked, that process is simple and durable.
Using the clear lens, spray the inside with spray-on tint. One or two light coats. It looks completely factory is durable and will not wear since the coating is on the INSIDE of the lens.
The spray on coating is made for this purpose and is available as most hobby / model stores.
Sorry I'm not more help, but it's what I did on my ST4s before I changed out the stocks.