I imagine that there are other brands...but if you are really going to use these, and they are tools, and you are going to use them on (perhaps very precious) blades....I suggest sticking with quality.
I can speak to the qualities of DMT products and I use their bench stones a LOT. I have one that is about 25 years old and I use it very frequently. If you want a decent tool that will last for a long time, I would (personally) buy the DMTs for 8-15 bucks (the range I usually see them for sale) and move on to the next question.
I hope that does not sound dickish or harsh...I just figure for even 15 bucks, this thing ought to serve you well for several years and MANY uses...so if you can justify a cup of coffee once in a while (like I do), it is pretty easy to justify something this inexpensive and potentially useful. A cheap imitation that loses the diamonds due to poor construction OTOH could be quite expensive.
That reminds me...Regardless of what you buy do NOT use pressure between the blade and the stone. The weight of the blade is all you need...excessive pressure will cause even the best stones to shed their diamonds.