Is this beautiful looking tree available for purchase in the GTA?
Golden Chain tree, Laburnum is a small genus with only 2 species (Laburnum anagroydes and Laburnum alpinum) and several cultivars. These beautiful small trees with cascading yellow flowers in late May/early June are native to the mountains of southern Europe.A quick search of online plant catalogues of Nurseries here in Ontario showed that Laburnun x watereri “Vossii”, a cross between L. anagroydes and L. alpinum, hardy to zone 6, that may reach a height of 15- 30 feet and a spread of 15-30 feet and Laburnum alpinum”Pendulum”, a weeping cultivar as the name indicates, also hardy in our Toronto climate with a height of 8-16 feet and a spread of 5-10 feet seem to be available.
As it is the policy of the Toronto Master Gardeners to not recommend single businesses I do recommend that you contact your local nursery to see if the cultivar of your choice is available. If not they will most likely be able to refer you to a possible source.
As you mention Chinese Gold Chain tree in your question I would like to add that there is a tree native to tropical Asia with the common name Golden Shower tree, Cassia fistula, with very similar spectacular flowers. However, this tree is not hardy to our climate here in Toronto.