Is there a non-bacterial source of lipopolysacchrides
Yes, there is. 

Lipopolysacchrides have been found in eukaryotes. The most famous example is green algae from Genus Chlorella.

According to Armstrong et al., (2002):


  The lipopolysaccharides (LPS) are ubiquitous components of the outer leaflet of the outer membrane of all gram-negative bacteria and are the principal toxic products of these organisms (1). The membrane anchor of LPS is lipid A, a central phosphodisaccharide unit that is attached to multiple -hydroxy fatty acid chains. LPS also contains the novel sugar, 3-deoxy-D-mannooctulosonic acid (KDO). Although generally believed to be restricted to prokaryotes, specifically the gram-negative eubacteria and the cyanobacteria (2), an LPS-like molecule has recently been reported from a eukaryote, the green alga Chlorella sp., strain NC64A. (emphases mine)


Also, for further discussion on LPS in eukaryotes, please see Histochemical Evidence for Lipopolysaccharide (Endotoxin) in Eukaryotes.

Source: 


Armstrong, P., Armstrong, M., Pardy, R., Child, A. and Wainwright, N. (2002). Immunohistochemical Demonstration of a Lipopolysaccharide in the Cell Wall of a Eukaryote, the Green Alga, Chlorella. The Biological Bulletin, 203(2), pp.203-204.