The problem with Timothy hay here in Australia is that it doesn't grow well in our climate so all the timothy hay you will find has been imported from other countries. As such it is usually very poor quality simply due to how long it is in transit, and often organic matter coming into Australia needs to be irradiated to eliminate any insects hitching a ride on the products.
I personally usually feed my guinea pigs Oaten hay, but on occasion when the Oaten hay is poor quality I will instead feed Wheaten hay. These are the only hay types grown locally to me. Avoid hays mixed with Lucerne, as Lucerne is another name for Alfalfa which is too high in calcium for guinea pigs. Make sure to visually inspect the bale before purchase for any signs of mould or excessive weed content (some weeds occasionally make it into a bale, but if you can visually see that there are plants that are not grass in the bale from the outside of the bale that is a sign of a bad bale).
Try finding a fodder store near you and ask them what hays they stock, my local fodder stores keep the hay in back sheds so you have to ask to view the bales, they are rectangle bales.