The problem with recommendations is that it is personal. What one person finds good or excellent is to another poor and unacceptable (too strong, bitter, etc.). The variety of plums used will also make a considerable impact on the taste of a plum based alcohol product as some are tart and others are sweet and juicy.
The only way to find a plum based spirit that one enjoys to try and sample a few (not expensive) types of plum based alcohols and see if one enjoys them.
In this sense, I would suggest that you try one of the following and then give us back your feedback.
A Slivovitz on the lower spectrum of alcohol content (35-40% alcohol) and not that of a higher volume content. This way the true natural flavors more be more apparent to one's taste buds.
Slivovitz, often called slivovitsa, is a plum brandy found throughout Eastern Europe. The word "slivovitz" is based on the Serbian and Croatian name for a type of plum used to create the drink. Major producers in the Balkans and in Central European nations like the Czech Republic make commercial versions of slivovitz. In rural areas, many people make homemade slivovitz using makeshift stills made from old barrels. In the Czech Republic, this kind of home distilling is now illegal, though lightly regulated community-owned stills are a legal alternative. In Serbia, slivovitz is almost always a part of important events such as celebration of a birth or a wedding reception. The liquor is usually drunk neat because it is said that the flavor of the plums is at its most noticeable at room temperature. Like other types of brandy, slivovitz has a sweet edge. Because so many varieties exist, strengths vary wildly. However, most good slivovitz is between 80 and 100 proof, though homemade versions can be much stronger than that. - Beyond whiskey: 7 exotic spirits worth a try
Pearl vodka has a plum vodka on the market based on natural flavors. Just follow the links to see if it is available in your region.
Bursting with the sweet, luscious flavor of summertime plums. The tartness of the skin quickly gives way to the jammy flesh within. Purple deliciousness ready to make a splash in your favorite warm-weather cocktail creations (35%). - Plum
Japanese plum wine is called a plum wine or Umeshu (梅酒) in Japan but in reality is a vodka based liqueur with green plums.
Plum Wine or Umeshu (梅酒) is a Japanese liqueur made by steeping fresh Japanese plum (ume) in shochu/white liquor [vodka] and sugar. The sweet and sour flavors with fruity aroma is very appealing and you can make many kinds of drinks with it! - Plum Wine (Umeshu) 梅酒 – ‘Midnight Diner: Tokyo Stories’
Although quite rare, real plum wine does exist and this is where I would start if new to plum drinks. For example Takara Plum Wine or Fuki Plum Wine is available in the USA.