
You can buy the stepping stones commercially, most of them should cost less than $25. A good resource for buying garden stepping stones would be Garden plaques at onlinediscountmart.com. They seem to have a huge variety of decorative stepping stones and the prices are not high.
You don't have to install stepping stones made out of concrete or cement alone, the other options you can try are listed below
You can buy some 100% rubber stepping stones for under $20, the best part is that they won't crack or rot under humid or dry conditions. They come in a lot of different decorative designs. The rubber is usually recycled one and it stands up to harsh weather, it's salt resistant and frost proof. It is easy to clean them up and relocate them.
Enough reasons for you to consider buying some of these. A good resources would be improvementscatalog.com
These can be a bit pricey, mostly above $30, but you can get some really artistic pieces. Cast aluminum garden stepping stones are becoming a vogue nowadays, these steppers come in various designs and shapes, some are even designed as shields.

There are online portals that create personalized stepping stones as per your requirements. For example epicmerchandise.com use slate stone to create unique pieces of art with the color, image and words of your choice. The pricing is very reasonable.
These stones make excellent gifts for your gardening friends or relatives, almost anyone who has a yard would love to have this gift. You can have their names embedded on the stone with an image of heart around it or just come up with some really funny or creative wordings.
You can even create inspirational stepping stones by embedding some beautiful proverbs or sutra.
Consider buying some pure mosaic stepping stones or a marble stone, these may be a little expensive but they look really sleek. You can even line up your garden with some natural boulders, be sure to dig them inside the soil so they have a strong foundation.
Whether you go in for concrete, rubber, aluminum, stone or mosaic, stepping stones you can always buy or make something decorative and aesthetic to add charm to your garden's decor.