Consult your owner's manual for the size needles your machine takes. Usually, it is 130/705 needles.
If so, you can purchase this size from most any fabric, sewing repair shops, or online vendors. There are many manufacturers who make needles, ie Schmetz, Organ, Klasse, as well as Singer. Schmetz is readily available most places in the US. (IMHO, Singer needles are made more specifically for Singer sewing machines and may not work as well on a non-Singer machine. Most Singer machine manuals recommend using only Singer needles and some sewists have experienced problems when using a different brand.) You may have to experiment with brands if you have any problems with a specific manufacturer brand.
However, there is much more to choosing needles for your machine than the size and brand. The most important choices are to choose needles that suit the thread & fabric you will be sewing. Be sure to read up on the needle types (from smallest 65/9 to heavier 110/18) and the design/shape that will work best for you, ie sharps (for woven fabric) or ball-point (for knits), quilting, topstitch, embroidery, microtex, stretch, denim, universal, leather, etc.
"The European metric sizing system for sewing machine needles is numbered from 60 to 110. The American sizing system is numbered from 8 to 18. For both sizing systems, the lower the number the finer the needle and the higher the number the larger the needle. Most needle companies show both sizes on the package." (quote from Singer)
In addition, if your machine is capable, you may also be able to use twin, triple needles, wing, wedge point needles. The following will be helpful when you make your purchasing choices:
All About Needles
FREE Printable PDF Guide to Schmetz Sewing Machine Needles