Availability depends on the method and material used to obtain the product. If it is not a general-purpose plastic or special material that is normally used, it can be available the next day or two after the order is placed. Or, if the order is placed first thing in the morning, it may be available the same day.
Note that there are fluctuations depending on the market in which the plastic is used, and materials that are normally available may become scarce and difficult to obtain depending on the market.
Even with common materials, some thicknesses and diameters that are not normally used will require a special order, which can take several days to complete.