Although those cars are not completely built, they could be used for cameo appearances at the Grand Prix.
Kiwi Supercars star van Gisbergen, who raced TRS early in his career, would be interested in competing.
"It is in a good time of the year for us in our off-season," the 27-year-old Red Bull Holden Racing Team driver told the Herald. "I'd love to do it.
"The reason it is mainly the European guys these days is that it is so expensive now. To find a one-off would be hard. I would love to have a go in it and see how I would go against all the young guys.
"It is very different now to when I used to do it. When I did it, there were two internationals and the rest were Kiwis and now it is the other way around.
"I would come back and race in New Zealand in a heartbeat - I love racing there."
Hartley and Bamber too have enjoyed massive success in Europe that culminated in their victory at the famous Le Mans 24 Hour race earlier this month. Both drivers are from the Manawatu region - ideal poster-boys for an event hoping to attract a big crowd.
Van Gisbergen's fellow Kiwi Supercars stars Fabian Coulthard and Scott McLaughlin could possibly be interested if their contracts allowed them a cameo with another manufacturer while former TRS champion Nick Cassidy is in the Toyota stable racing in Japan and could be lured back for a one-off drive.
Three Kiwis featured in the 2017 edition of the series with Marcus Armstrong, Taylor Cockerton and Brendon Leitch among the leading contenders but all are racing overseas and are yet to confirm whether they will return.
Promising youngsters Reid Harker and Liam Lawson tested TRS cars at Hampton Downs earlier this week and could be pushing for a drive this summer.
Series organisers are speaking to potential recruits about the 2018 series but are also being careful not to bite off more than they can chew with long-time category managers Barrie and Louise Tomlinson having stepped aside this year and replacements yet to be finalised.
